4 Replies Latest reply on Sep 2, 2016 3:32 AM by Beauty_and_dBest

    Duplicate IP in /etc/hosts

    Beauty_and_dBest

      Hi All,

       

      EBS R12.1.3

      OL5

      11gR2

       

      I check out /etc/hosts and I see duplicate IP entries?

       

      120.26.1.40 app.oracle.com app

      120.26.1.40 dbc.oracle.com dbc

       

       

       

      Is this the cause why our RDA diagnostics failed?

       

      Kind regards?

      jc

        • 1. Re: Duplicate IP in /etc/hosts
          handat

          nslookup will just resolve the first entry, ie 120.26.1.40 app.oracle.com app, but the second entry will be skipped over, so when you do a nslookup for app.oracle.com, it will succeed, but a nslookup for dbc.oracle.com would fail.

           

          If you want to resolve both names with the same IP, then you need to merge them into the same entry, ie

           

          120.26.1.40 app.oracle.com app dbc.oracle.com dbc

           

          • 2. Re: Duplicate IP in /etc/hosts
            Beauty_and_dBest

            Thanks Handat 

             

            So this is allowed in EBS? or This is not the reason why RDA test failed for this item?

             

            We have some failed items for our RDA health check

            Health Check/Validation for "Oracle E-Business Suite Release 12 (12.1.1) Preinstall (Linux x86 and x86_64)"

             

            One is

            A00420DNS LookupFAILEDnslookup IP_address
            A00420This rule checks that the host is registered correctly in the Domain Name Server (DNS).nslookup IP_addressThe DNS server failed to resolve the name using IP address.

             

             

             

            Kind regards,

            • 3. Re: Duplicate IP in /etc/hosts
              handat

              I am not sure what test RDA is performing. A DNS test usually check that a hostname resolves correctly to an IP, but it might go further and also do a reverse lookup, ie do a lookup on the IP and get the hostname back. This test would fail in many systems that don't have reverse dns configured. RDA might be doing this test as it appears to be checking for the IP address, ie

              A00420

              DNS LookupFAILEDnslookup IP_address

               

              So

               

              nslookup app.oracle.com should be successful and return the IP address, but nslookup 120.26.1.40 will not resolve if its just added to /etc/hosts

              It needs to be registered in the DNS server that is pointed to in  /etc/resolv.conf

               

              Check with your network admin whether your DNS supports reverse lookup and if so, whether it has the appropriate zone config with the arpa entries. FYI, Amazon R53 DNS server does not support reverse lookup in case you are using that.

              • 4. Re: Duplicate IP in /etc/hosts
                Beauty_and_dBest

                Hi Bashar,

                 

                We have also another instance in EC2. But it is working good.

                Well maybe it will fail RDA test as well, but we do not have problem with it

                 

                Still it has error in nslookup?

                 

                [root@erp ~]# cat /etc/hosts

                127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4

                100.31.14.118 erp.oracle.com erp

                 

                [root@erp ~]# cat /etc/sysconfig/network

                NETWORKING=yes

                #HOSTNAME=ip-100-31-14-118.ec2.internal

                HOSTNAME=erp.oracle.com

                NETWORKING_IPV6=no

                NOZEROCONF=yes

                 

                [root@erp ~]# cat /etc/resolv.conf

                # Generated by NetworkManager

                domain ec2.internal

                search ec2.internal oracle.com

                nameserver 100.31.0.2

                [root@erp ~]# nslookup erp.oracle.com

                Server:         100.31.0.2

                Address:        100.31.0.2#53

                 

                ** server can't find erp.oracle.com: NXDOMAIN

                 

                 

                 

                So how what do I do to make it pass?